Process of treating lubricating oil stock



Patented Jan. 14, 1936 UNITED STATES PROCESS OF TREATING LUBRICATING OILSTOCK John D. Fields, Los Angeles, Calif.

No Drawing. Application October 20, 1931, Serial No. 570,048

Claims. (Cl. 19634) The present invention relates to the production ofhigh quality lubricating mineral oil, which will be entirely stable andwill be free from tendency to thicken or form gum, during 5 use.

As is well known, lubricating mineral oil has heretofore been preparedfrom petroleum, after distilling off the lighter fractions, in severaldifferent manners. One method is to distill (some times steam distill orsome times vacuum distill or some times distill with steam under vacuum)the desired fraction from the petroleum. In other cases the residue inthe still after distilling off the lighter fraction is drawn off andeither filtered or purified chemically or both. The lubricatingdistillate or the residue is commonly purified first by treating withsulphuric acid, one or more batches being added, followed by settling,then sometimes washing with water,,then washing with a dilute causticalkali solution to neutralize acidity. Such purification does not removeall of the impurities present, as is proven by the fact that the oileven after such treatment frequently causes gumming of the bearings, andcauses gumming or thickening when the oil is used in internal combustionengines as a lubricant.

On account of the viscosity of lubricating oils, and more particularlythe heavy lubricating oils, it is difficult to completely treat the oilswith any kind of a chemical, and for that reason there is considerablewaste of acid and alkali in the purification of lubricating stock. Insome of the methods of purifying lubricating oil, it is customary to adda thinning agent such as naphtha or gasoline, or even kerosene, for example in the removal of amorphous wax (material similar to petrolatum)from the oil, by the Sharples process.

I have found that it is possible to economically purify the lubricatingoil, and take out all of the gum-forming impurities, by treatment withmetallic sodium. Instead of sodium other similar metals such as lithium,potassium, calcium, barium and strontium can be employed, this groupbeing hereinafter referred to as alkali metal. The said metal is used inthe metallic condition, and preferably at or below room temperature, andin any case at temperatures not exceeding 125 F.

The thinned lubricating oil can be passed as a continuous currentthrough one or more tanks, the alkali metal being preferably stationarytherein, and in a more or less comminuted condition, say in the form ofsmall bars or rods in order to expose a considerable amount of surfaceto the action of the oil mixture under treatment. The thinned oil shouldbe substantially free from water, and if the original stock containswater (as in the case of steam-distilled oil) it is advisable tothoroughly dehydrate the thinned oil before the same is brought intocontact with the sodium, otherwise the water would react with the sodiumand use up a large amount of sodium without any useful results beingthereby secured. The thinned oil may also be subjected to filtration ifthe same contains any sub stantial amount of insoluble materials. Theremoval of both the water and insoluble matter, if present, can beaccomplished by filtration and then passing the filtrate through asuitable centrifugal liquid separator, or in other well known manners.

ditions, and which was a highly viscous oil, was

first diluted with about twice its volume of a light petroleum naphtha,and the mixture well stirred. The mixture was found to containasubstantial proportion of water and a small amount of insoluble solidmaterial. This was filtered through a filter press, then passed througha centrifugal liquid separator to remove the suspended matter and water.The liquid was then passed through a tank containing metallic sodium,this being supported on grids above the bottom, the mixture of oil andnaphtha entering at the bottom of said tank and flowing upwardly throughthe same, and remaining in the tank about two hours. The sodium was inthe form of short bars about two inches long and a third of an inchsquare, in the form of a layer about a foot thick, so that in passingthrough the tank the oil mixture was brought into very intimate contactwith the surfaces of the sodium. Some of the impurities in the oil wereprecipitated on the surface of the sodium, as a somewhat gummy coating.Some of the impurities in the oil were apparently coagulated into agummy mass, a part of which settled into the bottom of the treatingtank, and another part of which settled out in a settling tank followingthe treating tank. After a large amount of the oil had been treated, itwas withdrawn from the settling tank, filtered and then run into a stillin which the naphtha was distilled off, the latter portion of thisdistillation being conducted under a vacuum of about five pounds persquare inch, in order to prevent any cracking of the oil, and thetemperature was carried up to about 500 F., While some steam was bubbledthrough, during the last twenty minutes of the distillation.

The lubricating oil, after cooling, was found to be of a very lightcolor, was found to be entirely stable when exposed to sun light for asubstantial period, was found to be free from gumming tendency when usedas a lubricant on shaft bearings and also when used as a lubricant in anautomobile engine.

It was found that a portion of the impurities coagulated from the oilwill deposit as a more or less gummy layer on the surfaces of the piecesof sodium. When this deposit gets thick it will slow down the action ofthe process, and for that reason it is advisable to provide means forrenewing the surfaces of the sodium, from time to time by dissolvingaway the accumulated ma.- terial therefrom. This can be accomplished bydiscontinuing the flow of the oil and solvent mixture, drawing off theoil and solvent from the treating tank, and flowing through the treatingtank a mixture of benzol and alcohol (for which purpose substantiallydehydrated denatured alcohol can be employed) it being preferable to usefrom 5 to 10% of the said alcohol in the benzol, and to flow the mixturethrough the tank until the surface of the sodium is found to be brightand free from deposit. The benzol and alcohol mixture removes thisdeposit very rapidly, and care should be taken not to continue thistreatment after the surface of the sodium has become bright, otherwisethe sodium will react chemically with the alcohol, with a loss ofsodium. For this purpose glass covered peep holes are provided in thetreating tank opposite the layer of sodium, for watching this operation.The sodium in being cut up and put into the treating tank may frequentlyacquire a thin film of oxide on its surface, and preferably I give thesodium a very short Wash with the benzol-alcohol mixture, beforeintroducing the solution of oil and thinning agent.

During the action practically none of the sodium is used up, and a givencharge of sodium is capable of refining an immense amount of thelubricating oil solution.

The lubricating oil product is entirely stable, and is free from gummingtendency, as stated above. It is also free from substances producing acorrosive action on metal bearings. A further and highly importantadvantage is that the refining loss is extremely low, amounting to onlya minor fraction of the refining loss which is encountered when refininga similar oil by the sulphuric acid and alkali method.

After the benzo-alcohol mixture has been used several times forrevivifying or 'reactivating the metallic sodium (alkali metal), thissolution can be run into a still and the benzol and alcohol distilledoff for reuse, leaving a valuable residue, which can be used in makingroad oil or for other purposes, so that there are no waste products tobe disposed of.

I have above spokenof distilling off the naptha from the lubricating oilafter the treatment of the solution of lubricating oil, with alkalimetal. This naptha having been treated with sodium in the process, isalso highly refied during the process. If this recovered naphtha ismixed with more of the lubricating oil, for the next run of the process,there is no impurity therein to be coagulated or precipitated on thealkali metal whereby cleaning of the latter by the benzol-alcoholmixture does not have to be so frequent.

It is also possible, instead of using naptha, gasoline, kerosene, etc.,as the solvent or thinning agent, to use a mixture of one or several ofthese mixed with a small fraction (say onefourth, more or less) ofbenzol, since such mixture will not act as a solvent to preventprecipitation of the gum-forming constituents of the oil and naptha,etc.

Where I have spoken of benzol, as a cleaning fluid for the alkali metal,I include also its homelogues, toluol, xylol, solvent naptha, etc., ormixtures thereof (benzol or its homologues, or single ring liquidaromatic hydrocarbon). Hydrogenated aromatic hydrocarbons, such ashexahydrobenzene, tetralin, etc., can be used in place of all or a partof the benzol. Ordinarily I prefer to use well dried (substantiallyanhydrous) 90% benzol, which as is well known contains a considerableproportion of toluol and other aromatic hydrocarbons.

I have referred to treating a specific lubricating oil distillate butvarious other lubricating oil cuts can be employed. In some cases thedistillate may be of about 24 B., while in other cases variousdistillates of gravities between about 18 and 36 B., can be treated bythe process, and it is understood that highly viscous oils will needmore of the thinning agent, and less viscous oils need less thereof.With a light lubricating stock of 26 B., I may use an equal volume ofgasoline, which will give a mixture of about 38 to 40 B., and ofsufficiently low viscosity.

I claim l. A process of treating a lubricating petroleum oil stock whichcomprises thinning same with a light petroleum hydrocarbon solvent, insuch proportions as to give a mixture of low viscosity, and thereafterflowing the mixture, in a substantially anhydrous condition, intointimate contact with a solid alkali metal in a comminuted state at notsubstantially above normal room temperature, until impurities thereinhave been coagulated, separating said oily materials and the coagulatedimpurities from each other, before chemical reaction of any substantialproportion of the alkali metal with hydrocarbon compounds is effected,and distilling said light petroleum hydrocarbon solvent, from thelubricating oil stock.

2. A process of treating a lubricating petroleum oil stock whichcomprises thinning same with a light petroleum hydrocarbon solvent, toproduce an intimate admixture therewith, removing water' from saidmixture, and thereafter treating the mixture, in a substantiallyanhydrous condition, with a solid alkali metal at not substantiallyabove normal room temperature, until impurities therein have beencoagulated, separating said oily materials and the coagulated impuritiesfrom each other, before chemical reaction of any substantial proportionof the alkali metal with hydrocarbon compounds is effected, anddistilling said light petroleum hydrocarbon solvent, from thelubricating oil stock, and thereafter when the alkali metal has becomecoated, contacting same with a mixture which is mostly a benzolhydrocarbon with a minor fraction only of a lower alcohol, until saidmetal becomes bright.

3. A process of treating a lubricating petroleum oil stock whichcomprises thinning same with a light petroleum hydrocarbon solvent, toproduce an intimate admixture therewith, removing material insoluble insaid solvent, and thereafter treating the mixture, in a substantiallyanhydrous condition, with a solid alkali metal at not substantiallyabove normal atmospheric temperature, until impurities therein have beencoagulated, separating said oily materials and the coagulated impuritiesfrom each other, before chemical reaction of any substantial proportionof the alkali metal with hydrocarbon compounds is effected, anddistilling said light petroleum hydrocarbon solvent, from thelubricating oil stock.

4. A process of treating a lubricating petroleum oil stock whichcomprises thinning same with a light petroleum hydrocarbon solvent, toproduce an intimate low viscosity free-flowing admixture therewith, andthereafter treating the mixture, in a substantially anhydrous condition,with a solid alkali metal at not substantially above atmospherictemperature, until impurities the solvent in a condition suitable forreuse in the process.

5. A process of refining a lubricating distillate from petroleum oil,which comprises mixing said 1 lubricating distillate with a lightreadily-volatile petroleum hydrocarbon distillate, and thereaftertreating the mixture, in a substantially anhydrous condition, with asolid alkali metal at not substantially above atmospheric temperature,.

until impurities therein have been coagulated, separating said oilymaterials and the coagulated impurities from each other, before chemicalreaction of any substantial proportion of the alkali metal withhydrocarbon compounds is,

efiected, and distilling said light petroleum hydrocarbon solvent, fromthe lubricating oil.

JOHN D. FIELDS.

